ggplot2：Heatmapプロット、選択したセル内のgeom_text配置

Question

私の実験では、ヒートマップを使用していくつかの日付情報を排他的に印刷したいのですが、何らかの理由でggplot2が 'その多くの欠落した観察を受け入れる。

これは私のプロットが現時点でどのように見えるか（多くの日付に）です。

どのようにgeom_textを2つの最初の列だけに制限することができますか？

サンプルコードはこちらを参照してください。

require(ggplot2) 
require(plyr) 
require(reshape) 

# create sample data 
set.seed(666) 
dfn <- data.frame(
Referral = seq(as.Date("2007-01-15"), len= 26, by="23 day"), 
VISIT01 = seq(as.Date("2008-06-15"), len= 24, by="15 day")[sample(30, 26)], 
VISIT02 = seq(as.Date("2008-12-15"), len= 24, by="15 day")[sample(30, 26)], 
VISIT03 = seq(as.Date("2009-01-01"), len= 24, by="15 day")[sample(30, 26)], 
VISIT04 = seq(as.Date("2009-03-30"), len= 24, by="60 day")[sample(30, 26)], 
VISIT05 = seq(as.Date("2010-11-30"), len= 24, by="6 day")[sample(30, 26)], 
VISIT06 = seq(as.Date("2011-01-30"), len= 24, by="6 day")[sample(30, 26)], 
Discharge = seq(as.Date("2012-03-30"), len= 24, by="30 day")[sample(30, 26)], 
Patient = factor(1:26, labels = LETTERS), 
openCase = rep(0:1, 100)[sample(100, 26)]) 

# set today's data for cases that do not have an Discharge date 
dfn$Discharge[ is.na(dfn$Discharge) ] <- as.Date("2014-01-30") 

mdfn <- melt(dfn, id=c('Patient', 'openCase'), variable_name = "Visit") 
names(mdfn)[4] <- 'Year' 

# order data in mdfn by 'Referral' in dfn 
mdfn$Patient <- factor(mdfn$Patient,levels = (dfn$Patient[order(dfn$Referral)]), 
ordered = TRUE) 

mdfn$Year2 <- ifelse(mdfn$Year != 0, 1, 0) 
mdfn$Year2[ is.na(mdfn$Year) ] <- 0 

mdfn$FWrap <- 'Core Measures' 
mdfn$FWrap[mdfn$Visit == 'Referral'] <- 'Referral' 
mdfn$FWrap[mdfn$Visit == 'VISIT05' | mdfn$Visit == 'VISIT06'] <- 'Optional Measures' 
mdfn$FWrap[mdfn$Visit == 'Discharge'] <- 'Discharge' 
mdfn$FWrap <- ordered(mdfn$FWrap, levels = c('Referral', 'Core Measures', 'Optional Measures', 'Discharge')) 

base_size <- 9 
m2 <- ggplot(mdfn, aes(Visit, Patient)) + 
geom_tile(aes(fill = Year2), colour = "gray") + 
scale_fill_gradient(low = "white", high = "steelblue") 
m2 + theme_grey(base_size = base_size) + labs(x = "", y = "") + 
scale_x_discrete(expand = c (0, 0)) + scale_y_discrete(expand = c(0, 0)) + 
opts(legend.position = "none", axis.ticks = theme_blank(), 
axis.text.x = theme_text(size = base_size * 0.8, angle = 330, hjust = 0, 
colour = "grey50")) + facet_grid(~ FWrap, scales = "free", space="free") + 
geom_text(aes (label=format(Year, "%b. %d, %Y")), size=3, colour='white') 

# this is how I thought I could solve it. 
mdfn$Yearlabel <- mdfn$Year 
mdfn$Yearlabel[mdfn$Visit != 'Referral' & mdfn$Visit != 'VISIT01'] <- NA 
# mdfn[,c(4,5,7,3)] 

m2 <- ggplot(mdfn, aes(Visit, Patient)) + 
geom_tile(aes(fill = Year2), colour = "gray") + 
scale_fill_gradient(low = "white", high = "steelblue") 
m2 + theme_grey(base_size = base_size) + labs(x = "", y = "") + 
scale_x_discrete(expand = c (0, 0)) + scale_y_discrete(expand = c(0, 0)) + 
opts(legend.position = "none", axis.ticks = theme_blank(), 
axis.text.x = theme_text(size = base_size * 0.8, angle = 330, hjust = 0, 
colour = "grey50")) + facet_grid(~ FWrap, scales = "free", space="free") + 
geom_text(aes (label=format(Yearlabel, "%b. %d, %Y")), size=3, colour='white') 

Answer 1

p = ggplot(mdfn, aes(Visit, Patient)) + 
    geom_tile(aes(fill = Year2), colour = "gray") + 
    scale_fill_gradient(low = "white", high = "steelblue") + 
    theme_grey(base_size = base_size) + 
    labs(x = "", y = "") + 
    scale_x_discrete(expand = c(0, 0)) + 
    scale_y_discrete(expand = c(0, 0)) + 
    opts(legend.position = "none", axis.ticks = theme_blank(), 
     axis.text.x = theme_text(size = base_size * 0.8, angle = 330, 
     hjust = 0, colour = "grey50")) + 
    facet_grid(~ FWrap, scales = "free", space="free") 

s = subset(mdfn, Visit %in% c("Referral","VISIT01")) 
p + geom_text(aes(label=format(Year, "%b. %d, %Y")), data = s, 
       size=3, colour = 'white')